The invention concerns a band saw blade with teeth having a tooth point with a tooth edge, a tooth face on the front side of the tooth as viewed in the direction of sawing, a tooth back behind the tooth edge, and a tooth bottom between the tooth face on each tooth and the tooth back on the next tooth in front of said each tooth, and tooth gullets, wherein a tooth gullet is defined as the space between the tooth edges of two adjacent teeth, said saw blade having two planar sides; a right hand side and a left hand side when the saw blade is viewed obliquely from above in the direction of sawing, wherein said tooth edge extends between a right hand tooth corner and a left hand tooth corner with reference to said viewing direction.
Saw teeth of band saw blade work as tiny planing tools generating chips at high speed by planing and/or tearing, the chips being collected and removed in the tooth gullets. The development of increasingly efficient band saws has aimed at further developing this planing and/or tearing function of band saw blades. It is a typical feature of band saw blades that the teeth are set or swaged, so that the kerf will be somewhat wider than the blade is thick. The kerf is formed due to their milling away material.
It is also typical for band saw blades that they vibrate and give rise to noise at a volume which in many cases can be uncomfortably high. Further, the surfaces of the kerfs will be grooved or otherwise uneven, which requires considerable finishing in those cases when smooth surfaces are desired. Among other drawbacks can be mentioned that setting and swaging cause wide kerfs and hence substantial losses of material.
It is the purpose of the invention to provide a band saw blade which saws very silently, which does not give rise to inconvenient vibrations, which gives surfaces having a good smoothness and thin, material-saving kerfs when sawing in e.g. wood, plastic, meat and metal.
Surprisingly, these effects can be achieved with a saw blade according to the invention. A band saw blade designed in this way, wherein the saw blade in the region of the tooth gullets following directly upon one another are bevelled alternatingly to the left and to the right, has surprisingly turned out not to require any setting or swaging of the teeth in order to run freely in the kerf that is being established. The sawing is extremely easy to perform, without noticeable vibration, and very silent and gives cuts with good surface smoothness when sawing in for example wood, plastics, and metal. Without binding the invention to any specific theory, it can be assumed that the saw blade combines the planing operation of the teeth with the operation of tools which cut like knives.
Especially favourable results have been achieved when forming each tooth face F1, F2 slightly concave. The hook angle a should preferably not exceed 15xc2x0, such that the strength of the teeth of the band saw blade is kept within acceptable limits. On the other hand the hook angle a should not be less than 1xc2x0 in order to provide for a desired milling action. Preferably the hook angle is between 2-10xc2x0, more preferred about 3-8xc2x0. Moreover the tooth face F1, F2 should be angled in relation to the extension of the band saw blade to form an angle f1 which also is less than 15xc2x0 but at least 1xc2x0, preferably 2-10xc2x0, more preferred about 3-8xc2x0. Also the bevelled surface S1 may be angled at about the same amount, i.e. xcex2 is less than 15xc2x0, but more than 1xc2x0, preferably 2-10xc2x0 and more preferred about 3-8xc2x0. Finally the same relation may be desirable in relation to the extension of the tooth edges E1, E2 being alternately angled in relation to the horisontal plane along the band saw blade, i.e. forming an angle xcex3 which is less than 15xc2x0 but more than 1xc2x0, preferably 2-10xc2x0, more preferred about 3-8xc2x0. Finally it has been noted that the structural strength of the band saw blade according to the invention may be further improved if the tooth back H1, H2 is formed slightly convex.
Successful experiments have been performed with saw blades designed in the above described manner, through sawing in fresh victuals, such as meat and fish etc, and in plastic, wood and comparatively soft metals, such as brass, wherein the saw blade consisted of a conventional, hardened carbon steel. It can be assumed that the same good results can be achieved also when sawing in harder materials, such as steel and other hard metals, if at least the saw teeth, or those parts thereof which are subjected to wear, consist of more qualified materials than hardened carbon steel, such as high speed steel, Stellite or cemented carbide.
In view of the successful experiments that have been performed with a saw blade designed in the above described way, one can also conceive that substantial improvements in comparison with prior art saw blades can be achieved also when the bevelled region has a smaller extension than what has been described above. It is, however, the opinion of the inventors that the bevelled region shall extend from the tooth edge of the first tooth point in the rear end of the first tooth gullet, down the tooth face and to at least the tooth bottom. Generally speaking, it can therefore be stated that the said region shall be bordered to the right by a first line which extends from a rear foot point defined by the right hand tooth corner of the first tooth edge or by a point on the first tooth edge, which point is nearer the right hand tooth corner than the left one, to a front foot point which borders on the left hand side of the saw blade in the region of the first tooth gullet or is a point on the tooth edge on the next tooth in front of said first tooth, to the left by the border line against the left planar side of the saw blade, and forwards by said first line and/or by the tooth edge of said next tooth when the front foot point of said first line lies on said next tooth edge; that the saw blade, within a region of a second tooth gullet between a second tooth and a next tooth in front of said second tooth is bevelled in the same way as in the first tooth gullet but instead to the right, and that the saw blade within the region of first and second tooth gullets between first or second teeth, on one hand, and teeth in front thereof, on the other hand, along the length of the saw blade, are bevelled in the said way alternatingly to the left and to the right in said first and second tooth gullets.
Probably, best results are achieved if all teeth and tooth gullets are designed according to the invention, wherein the material in the region of tooth gullets following consecutively directly after one another are bevelled alternatingly to the left and to the right. The invention, however, also can conceive that the saw blade within two or more tooth gullets following subsequently after each other is bevelled to the left, followed by a number of tooth gullets in which the saw blade is bevelled to the right and so on, repeatedly, although the inventors do not consider that that gives any significantly favourable effect.
The successful experiments with saw blades according to the invention have been performed with band saw blades.
Further characteristic features and aspects of the invention will be apparent from the appending claims and from the following description of the successfully tested embodiment and some other, conceivable embodiments.